Project description:Systematic analyses of the temporal dynamics of transcriptomes and chromatin landscapes of macrophages during timecourse of TLR4-mediated inflammatory response. As a multifunctional effector cell, macrophages play pivotal roles in both the induction and resolution components of varied inflammatory processes. During the course of an inflammation response, macrophages engage in a homeostatic program characterized by tightly coordinated modulation of temporal outputs of both lipid metabolism and inflammation. We demonstrate inversely biphasic temporal dynamics of specific fatty acid metabolic and inflammatory gene expression profiles, associated with concordant temporal reprogramming of macrophage fatty acid profiles. In part, the late phase of the macrophage inflammatory response is characterized by tailoring of fatty acid related gene expressions, facilitating both significant induction of anti-inflammatory unsaturated fatty acid production and associated resolution of inflammation. We demonstrate the biphasic temporal dynamics of macrophage inflammation, specifically anti-inflammatory omega-3 and omega-9 unsaturated fatty acid levels, are transcriptionally driven genome-wide by an unexpected shift from an LXR to SREBP1-dominant regulatory program in the late phase inflammatory response. Collectively, our findings reveal a novel Srebp1-driven mechanism allowing the intimate inverse temporal relationship between the transcriptional regulation of inflammatory and fatty acid metabolic outputs; whereby modulation key transcriptional regulators (LXR, SREBP1 and NF-kB) of these pathways coordinate appropriate temporal tailoring of local enhancer associated reprogramming and eventual pathway regulatory interactions, during the course of TLR4-dependent inflammatory response in macrophages. This specific Srebp-driven, temporal reprogramming of macrophage fatty acid metabolism, characterized by late phase induction of anti-inflammatory unsaturated fatty acid production, is necessary for appropriate resolution of inflammation. Thus, this study suggests that selective reprogramming of macrophage lipid metabolism can serve as a viable therapeutic intervention aimed at ameliorating chronic inflammation and varied metabolic syndrome associated states.
Project description:Macrophages are critical immune cells in inflammatory diseases and their differentiation and function are tightly regulated by epigenetic alterations. H3K79 methylation is an epigenetic modification associated with active gene expression and DOT1L is the only histone methyltransferase for H3K79. Here we determine the role of DOT1L in macrophages by applying a selective DOT1L inhibitor in mouse and human macrophages and using myeloid-specific Dot1l deficient mice. We found that DOT1L directly regulates macrophage function by controlling lipid biosynthesis gene programs including central lipid regulators like sterol regulatory element-binding proteins SREBP1 and SREBP2. DOT1L inhibition also leads to macrophage hyperactivation which is associated with disrupted SREBP pathways. In vivo, myeloid Dot1l deficiency reduces atherosclerotic plaque stability and increases the activation of inflammatory plaque macrophages. Our data show that DOT1L is a crucial regulator of macrophage inflammatory responses and lipid regulatory pathways and suggests a high relevance of H3K79 methylation in inflammatory disease.
Project description:Macrophages are critical immune cells in inflammatory diseases and their differentiation and function are tightly regulated by epigenetic alterations. H3K79 methylation is an epigenetic modification associated with active gene expression and DOT1L is the only histone methyltransferase for H3K79. Here we determine the role of DOT1L in macrophages by applying a selective DOT1L inhibitor in mouse and human macrophages and using myeloid-specific Dot1l deficient mice. We found that DOT1L directly regulates macrophage function by controlling lipid biosynthesis gene programs including central lipid regulators like sterol regulatory element-binding proteins SREBP1 and SREBP2. DOT1L inhibition also leads to macrophage hyperactivation which is associated with disrupted SREBP pathways. In vivo, myeloid Dot1l deficiency reduces atherosclerotic plaque stability and increases the activation of inflammatory plaque macrophages. Our data show that DOT1L is a crucial regulator of macrophage inflammatory responses and lipid regulatory pathways and suggests a high relevance of H3K79 methylation in inflammatory disease.
Project description:Macrophages are critical immune cells in inflammatory diseases and their differentiation and function are tightly regulated by epigenetic alterations. H3K79 methylation is an epigenetic modification associated with active gene expression and DOT1L is the only histone methyltransferase for H3K79. Here we determine the role of DOT1L in macrophages by applying a selective DOT1L inhibitor in mouse and human macrophages and using myeloid-specific Dot1l deficient mice. We found that DOT1L directly regulates macrophage function by controlling lipid biosynthesis gene programs including central lipid regulators like sterol regulatory element-binding proteins SREBP1 and SREBP2. DOT1L inhibition also leads to macrophage hyperactivation which is associated with disrupted SREBP pathways. In vivo, myeloid Dot1l deficiency reduces atherosclerotic plaque stability and increases the activation of inflammatory plaque macrophages. Our data show that DOT1L is a crucial regulator of macrophage inflammatory responses and lipid regulatory pathways and suggests a high relevance of H3K79 methylation in inflammatory disease.
Project description:Macrophages are critical immune cells in inflammatory diseases and their differentiation and function are tightly regulated by epigenetic alterations. H3K79 methylation is an epigenetic modification associated with active gene expression and DOT1L is the only histone methyltransferase for H3K79. Here we determine the role of DOT1L in macrophages by applying a selective DOT1L inhibitor in mouse and human macrophages and using myeloid-specific Dot1l deficient mice. We found that DOT1L directly regulates macrophage function by controlling lipid biosynthesis gene programs including central lipid regulators like sterol regulatory element-binding proteins SREBP1 and SREBP2. DOT1L inhibition also leads to macrophage hyperactivation which is associated with disrupted SREBP pathways. In vivo, myeloid Dot1l deficiency reduces atherosclerotic plaque stability and increases the activation of inflammatory plaque macrophages. Our data show that DOT1L is a crucial regulator of macrophage inflammatory responses and lipid regulatory pathways and suggests a high relevance of H3K79 methylation in inflammatory disease.
Project description:Metabolic reprogramming has emerged as a crucial regulator of immune cell activation but how systemic metabolism influences immune cell metabolism and function remains to be investigated. To investigate the effect of dyslipidemia on immune cell metabolism, we performed in-depth transcriptional, metabolic and functional characterization of macrophages isolated from hypercholesterolemic mice. Systemic metabolic changes in such mice alter cellular macrophage metabolism and attenuate inflammatory macrophage responses. In addition to diminished maximal mitochondrial respiration, hypercholesterolemia reduces the LPS-mediated induction of the pentose phosphate pathway (PPP) and the Nrf2-mediated oxidative stress response. Our observation that suppression of the PPP diminishes LPS-induced cytokine secretion supports the notion that this pathway contributes to inflammatory macrophage responses. Overall, this study reveals that systemic and cellular metabolism are strongly interconnected, together dictating macrophage phenotype and function.
Project description:Background and Aims: Inflammasome-mediated caspase-1 activity regulates the maturation and release of the pro-inflammatory cytokines interleukin (IL)-1M-CM-^_ and IL-18. Recently, we showed that caspase-1 deficiency strongly reduces high fat diet-induced adiposity although the mechanism is still unclear. We now aimed to elucidate the mechanism by which caspase-1 deficiency reduces modulates resistance to high fat diet-feeding fat accumulation in adipose tissue by focusing on the role of caspase-1 in the regulation of triglyceride (TG)-rich lipoprotein metabolism. Methods: Caspase-1 deficient and wild-type mice (both C57Bl/6 background) were used to determine postprandial TG kinetics, intestinal TG absorption, VLDL-TG production as well as TG clearance, all of which strongly contribute to the supply of TG for storage in adipose tissue. Micro-array and qPCR analysis were used to unravel intestinal and hepatic metabolic pathways involved. Results: Caspase-1 deficiency reduced the postprandial response to an oral lipid load, while tissue specific clearance of TG-rich lipoproteins was not changed. Indeed, an oral olive oil gavage containing [3H]TG revealed that caspase-1 deficiency significantly decreased intestinal chylomicron-TG production and reduced the uptake of [3H]TG-derived FA by liver, muscle, and adipose tissue. Similarly, caspase-1 deficiency reduced the hepatic VLDL-TG production without reducing VLDL-apoB production, despite an elevated hepatic TG content. Pathway analysis revealed that caspase-1 deficiency reduces intestinal and hepatic expression of genes involved in lipogenesis. Conclusions: Absence of caspase-1 reduces assembly and secretion of TG-rich lipoproteins, thereby reducing the availability of TG-derived FA for uptake by peripheral organs including adipose tissue. We anticipate that caspase-1 represents a novel link between innate immunity and lipid metabolism. Keywords: Expression profiling by array Wild-type (WT) and Casp1-null mice were maintained at lab chow. Animals, aged between 14 and 16 weeks (n=3 per genotype), were killed and liver and intestinal segments were removed. Livers were isolated from mice that were fasted over night, whereas intesines were removed from mice 2 hrs after they received an oral lipid load.Total RNA was isolated and subjected to gene expression profiling.